• State Resolved
  • Locked Locked
  • Replies 12 replies
  • Answers 6 answers
  • Subscribers 40 subscribers
  • Views 9670 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TINA/Spice/TINA-TI: Simulation of Buck converter power stage and feedback compensation in open and close loop

VikasDabas
Prodigy 220 points
Part Number: TINA-TI

Tool/software: TINA-TI or Spice Models

Dear all,

I have used tina tool for several time. I am making a buck converter. i need to calculate the transfer function and plot it for checking of frequency responce of my circuit.

help me simulate it using any simple circuit. I just need to see if my feedback circuit is stable or not.

Vikas Dabas

  • 0
    TI__Expert 3140 points

    Hi Vikas,

    Please consider this document for buck converter frequency analysis http://www.ti.com/lit/an/slva301/slva301.pdf  

    Also could you please share your .tsc file with us?

    Thanks & Regards,

    Arpan Gupta 

  • 0 in reply to Arpan Gupta
    Prodigy 220 points

    Arpan Gupta said:

    Please consider this document for buck converter frequency analysis http://www.ti.com/lit/an/slva301/slva301.pdf  

    Thanks for sharing this document.

    Arpan Gupta said:

    Also could you please share your .tsc file with us?

    This is what i asked you to share.

    As i can see the circuit:

    Now, I can make and test above two blocks referred as Power Stage and Feedback stage,

    The main problem is to test the whole circuit together. I do not have this Modulator and opamp model with me.

    So i request you to provide tina model for modulator and opamp..

    also suggest what opamp is best to use in such feedback test circuits while testing this circuit independently.

    .

  • 0 in reply to VikasDabas
    TI__Expert 3140 points

    Hi Vikas,

    We have configured the above circuit in TINA-TI. PFA the test bench BUCK_CONVERTER_FREQ_ANALYSIS.TSC

    Kindly note the following

    1. Modulator gain is kept 1/Vramp i.e 1/0.85 as per the above schematic 

    2. We have used an ideal OPAMP (implemented with VCVS only with DC gain of 1MEG).

    Below is the simulation result (loop response).

    Thanks & Regards,

    Arpan Gupta

  • 0 in reply to Arpan Gupta
    Prodigy 220 points
    Dear Arun,
    Thanks for sharing the schematic with me. One thing i need to know about this schematic is that weather i can use this schematic for testing my feedback loop. Say type 2 or type 3.
    Also one thing i need to know, what is the gain of opamp used in Buck controller IC's. Any example will be better.
  • 0 in reply to VikasDabas
    Prodigy 220 points

    Dear Arun,

    One more thing, this model is just to simulate the AC characterstics. How can i see the output and input, ripples and other things.

    How do i apply some input and get some output using this model?

    Or suggest me some other model that can show the output voltage.

  • 0 in reply to VikasDabas
    TI__Expert 3140 points

    Hi Vikas,

    The test schematic shared with you can be used to analyse the frequency response of the loop (the analysis includes type-2 or type-3 compensation of error amplifier).

    Please consider the part TPS57114-Q1as an example ( http://www.ti.com/lit/ds/symlink/tps57114-q1.pdf ). Below is the details of error amplifier (from page no. 5 of  datasheet).

    We can observe that the transconductance of the error amplifier in startup and steady state are provided in the above table. 

    Thanks & Regards,

    Arpan Gupta

  • 0 in reply to VikasDabas
    TI__Expert 3140 points

    Hi Vikas,

    Please consider the part TPS57114-Q1. Kindly use the link http://www.ti.com/product/TPS57114-Q1/toolssoftware to download the TPS57114-Q1 TINA-TI transient reference design. 

    You will be able to analyse input and output behaviour of the model using the above test bench. Kindly note that using the above transient model you will not be able to run AC analysis.

    Thanks & Regards,

    Arpan Gupta

  • 0 in reply to Arpan Gupta
    Prodigy 220 points

    Dear Arpan,

    First, Example circuit, which contains specific IC, does not help me in any case. It is because IC behaviour is not same for all IC's. It changes a lot with IC to IC. Therefor you have separate model for each IC. If wrong, kindly suggest.

                      For example circuit i mean is to include circuit same as frequency response model, which is generic.

    Second: I do not understand the unit of gain. In Tina-ti model, you said gain in 1M for feedback opamp.

                    Now it is showing 245uS. How Gain can be shown in time? Kindly elaborate.

    Third: My question is still Unanswered, I need to check frequency analysis of some filter and feedback loop, with input and output voltage and current.

                 How can i check both of them in same circuit?

             From your last post, i think you do not have such model. But, i might have seen such model in a pdf, i did not recall where. 

    Fourth: What about Gain and Phase gain calculation?

                  Can you suggest me some way to calculate the gain and phase margin directly.

                  You can see this image as reference and suggest me the gain and phase margin. Here i suspect Phase margin is 50deg, But cannot identify gain margin.

  • 0 in reply to VikasDabas
    TI__Expert 3140 points

    Hi Vikas,

    Please find my answers below

    1. We do not have a generic model to analyse frequency response. But you can develop your own using the TINA-TI test bench I shared with you on 16/10/2017.

    2. The error amplifier we referred is transconductance error amplifier or Gm error amplifier. Error amplifier's transconductance is 245uS (micro Siemens). If we multiply the value of transconductance with error amplifier's output impedance, we get the value of DC gain of the error amplifier. DC gain of error amplifier is dimensionless.

    3. If you want to check the frequency response of the loop, choose Analysis--> AC analysis--> AC transfer characteristics. In the same test bench, if you want to see the nodal voltages choose Analysis--> DC analysis--> Calculate nodal voltages. Kindly note that the TINA-TI circuit I shared with you on 16/10/2017 will support only AC and DC analysis. It will not support transient analysis.

    4. Please consider the below simulation results to calculate phase and gain margin

    Thanks & Regards,

    Arpan Gupta

  • 0 in reply to Arpan Gupta
    Prodigy 220 points
    Dear Arpan,
    Is this system stable? It has negative gain.
    Can you share any model that has type 3 feedback with compensation connected to feedback resistors? TPS57114 has compensation with respect to ground.

    I have tested DC analysis, it is not that helpful.
  • 0 in reply to VikasDabas
    TI__Expert 3140 points

    Hi Vikas,

    Gain margin= 0-Gain(at phase crossover frequency)=0-(-33.39)dB= 33.39dB and phase margin= 56.89deg. Hence the system is stable.

    Also all our available models can be found using the link below. You can search for a part which has type-3 compensation (kindly refer to part's datasheet to find the type of compensation used).

    Thanks & Regards,

    Arpan Gupta 

  • 0 in reply to VikasDabas
    TI__Expert 3140 points
    Hi Vikas,

    Gain margin= 0-Gain(at phase crossover frequency)=0-(-33.39)dB= 33.39dB and phase margin= 56.89deg. Hence the system is stable.

    Also all our available models can be found using the link below. You can search for a part which has type-3 compensation (kindly refer to part's datasheet to find the type of compensation used).

    Thanks & Regards,

    Arpan Gupta